(a) Field of the Invention
The present invention relates to a fuel cell stack. More particularly, the present invention relates to a separator positioned closely adjacent to a membrane-electrode assembly and a manufacturing method thereof.
(b) Description of the Related Art
In general, a fuel cell is a device that generates electrical energy by an oxidation reaction of a fuel and a reduction reaction of oxygen that is separately supplied. The fuel is a liquid or a gas fuel, or may include hydrogen cracked from the liquid fuel or the gas fuel.
A fuel cell stack is a structure in which several to several tens of electricity generation units each including a membrane-electrode assembly and a separator are stacked. The separator is disposed on both sides of the membrane-electrode assembly and forms a channel to supply the fuel or oxygen to one surface toward the membrane-electrode assembly. Also, the separator is formed of a conductive material and couples a cathode of one membrane-electrode assembly and an anode of the neighboring membrane-electrode assembly in series.
Under an operation of the fuel cell stack, water is generated by the reduction reaction of oxygen by the cathode in the membrane-electrode assembly. However, this water is not smoothly exhausted to the outside through the channel of the separator but is deposited on an inner wall of the channel. The water that is formed in the separator disturbs the mobility of hydrogen and oxygen such that oxygen may not be smoothly provided to the cathode of the membrane-electrode assembly, and as a result, chemical reaction efficiency of the fuel cell is largely deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.